What does Charles's law say?
Hold pressure steady and heat a gas: it expands. Cool it and it contracts. Volume is directly proportional to absolute temperature: V₁/T₁ = V₂/T₂. Each degree adds about 1/273 of the volume at 0 °C; extrapolate backward and the volume hits zero at −273.15 °C—absolute zero (0 K).
What are some examples?
Hot-air balloons rise because heated air expands and becomes less dense. A dented ping-pong ball pops back out in hot water, and tire pressure drops on cold winter mornings. Combine it with Boyle's law and you get the combined gas law, PV/T = constant.
FAQ
- Can I use Celsius?
- No—always convert to kelvin (°C + 273) first.
- How is it different from Gay-Lussac's law?
- Gay-Lussac's law usually refers to pressure vs. temperature at constant volume.
Sources reviewed: 2026-10-25
References
- Gay-Lussac, J. L. (1802). Recherches sur la dilatation des gaz et des vapeurs. Annales de Chimie, 43, 137–175.
- Atkins, P., & de Paula, J. (2014). Atkins' Physical Chemistry (10th ed.). Oxford University Press.